Assembly for Actuating a Downhole Tool

ABSTRACT

A valve seat assembly for actuating a connected downhole tool. The connected downhole tool may be mechanically connected, such as a sleeve positionable between flow ports through a housing, or hydraulically connected, such as through establishing a fluid communication path to the tool to cause actuation thereof. The valve seat assembly generally has a seating element with an having an inlet and an outlet; and a counting element configured to keep a tally of the number times a first pressure at the inlet exceeds a second pressure at the outlet by at least a pre-determined amount.

CROSS-REFERENCES TO RELATED APPLICATIONS

This original nonprovisional application claims the benefit of U.S.provisional application Ser. No. 61/475,333 filed Apr. 14, 2011 andentitled “Downhole Tool and System for Producing Hydrocarbons,” which isincorporated by reference herein. This application also claims thebenefit of U.S. application Ser. No. 13/423,154, filed Mar. 16, 2012 andentitled “Downhole System and Apparatus Incorporating Valve AssemblyWith Resilient Deformable Engaging Element,” and Ser. No. 13/423,158,filed Mar. 16, 2012 and entitled “Multistage Production SystemIncorporating Downhole Tool With Collapsible or Expandable C-Ring,” bothof which are incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

1. Field of the Invention

The present invention relates to oil and natural gas production. Morespecifically, to systems, tools, and methods used in fracturing and/orproducing hydrocarbons in one or more stages in a hydrocarbon-producingwell.

2. Description of the Related Art

In hydrocarbon wells, fracturing (or “fracing”) is a technique used bywell operators to create and/or extend a fracture from the wellboredeeper into the surrounding formation, thus increasing the surface areafor formation fluids to flow into the well. Fracing can be accomplishedby either injecting fluids into the formation at high pressure(hydraulic fracturing) or injecting fluids laced with round granularmaterial (proppant fracturing) into the formation.

Fracing multiple-stage production wells requires selective actuation ofdownhole tools, such as fracing valves, to control fluid flow from thetubing string to the formation. For example, U.S. Published ApplicationNo. 2008/0302538, entitled Cemented Open Hole Selective Fracing Systemand which is incorporated by reference herein, describes embodiments forselectively actuating a fracing sleeve that incorporates a shiftingtool. The tool is run into the tubing string and engages with a profilewithin the interior of the valve. An inner sleeve may then be moved toan open position to allow fracing or to a closed position to preventfluid flow to or from the formation.

That same application describes a system using multiple ball-and-seattools, each having a differently-sized ball seat and corresponding ball.Ball-and-seat systems address some of the drawbacks of shifting toolsbecause they do not require running such shifting tools thousands offeet into the tubing string. Ball-and-seat systems can be designed toallow a one-quarter inch difference between sleeves and the innerdiameters of the seats of the valves within the string. For example, ina 4.5-inch liner, balls from 1.25-inches in diameter to 3.5-inches indiameters can be dropped in one-quarter inch or one-eighth inchincrements, with the smallest ball seat positioned in the last valve inthe tubing string. This, however, can limit the number of valves thatcan be used in a given tubing string because in these systems each ballis designed to actuate a single valve and the size of the liner maylimit the number of valves with differently-sized ball seats.

BRIEF SUMMARY

The present invention increases system effectiveness and reducesmechanical risk, thereby increasing system reliability while loweringcost. Operators need not be concerned about impacting the shifting ballinto a seat at too high of a rate or pressure which may lead in somecases to a failure of the ball or sleeve.

The present invention contemplates a valve seat assembly for actuating aconnected downhole tool. The connected downhole tool may be mechanicallyconnected, such as a sleeve positionable between flow ports through ahousing, or hydraulically connected, such as through establishing afluid communication path to the tool to cause actuation thereof. Thevalve seat assembly generally has a seating element with an having aninlet and an outlet; and a counting element configured to keep a tallyof the number times a first pressure at the inlet exceeds a secondpressure at the outlet by at least a pre-determined amount.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a sectional side elevation of a preferred embodiment of theapparatus of the present invention in a neutral state.

FIG. 1A is an enlarged view of window 1A of FIG. 1.

FIGS. 2A and 2B are isometric front and rear views of the slotted membershown in FIG. 1.

FIG. 2C shows the footprint of the slot formed in the exterior surfaceof the slotted member shown in FIGS. 2A and 2B.

FIG. 3 is intentionally omitted.

FIG. 4 is a side sectional elevation of the embodiment shown in FIG. 1in a shifted state.

FIG. 4A is an enlarged view of window 4A of FIG. 4.

FIG. 5 is a side sectional elevation of the embodiment shown in FIG. 1in an actuated state.

FIG. 5A is an enlarged view of window 5A of FIG. 5.

FIG. 6 is a side elevation of a system incorporating multiple portedsleeves of the preferred embodiment shown in FIG. 1.

FIG. 7 is a sectional elevation of a pressure chamber and firing pin ofa second embodiment of the invention.

FIG. 8 is a sectional elevation of the firing assembly and pressurechamber shown in FIG. 7 wherein the firing pin has been released and hasimpacted the primer.

FIG. 9 shows components of yet another embodiment of a valve assemblythat comprises a C-ring.

FIG. 10 is a front elevation for the C-ring of FIG. 9

FIG. 11 is a sectional view through line 11-11 of FIG. 9.

FIG. 12 shows the embodiment of FIG. 9 with the sleeve and valveassembly in a shifted position.

FIG. 13 is a sectional view through line 13-13 of FIG. 12.

FIG. 14 shows the embodiment of FIG. 9 with the sleeve and valveassembly in an actuated position.

DETAILED DESCRIPTION

When used with reference to the figures, unless otherwise specified, theterms “upwell,” “above,” “top,” “upper,” “downwell,” “below,” “bottom,”“lower,” and like terms are used relative to the direction of normalproduction through the tool and wellbore. Thus, normal production ofhydrocarbons results in migration through the wellbore and productionstring from the downwell to upwell direction without regard to whetherthe tubing string is disposed in a vertical wellbore, a horizontalwellbore, or some combination of both. Similarly, during the fracingprocess, fracing fluids move from the surface in the downwell directionto the portion of the tubing string within the formation.

FIG. 1 depicts a valve seat assembly 22 in which the tool to be actuatedis a ported sleeve. A tubing string section 26 provides a fluidcommunication path between the ported sleeve assembly 22 and otherdownhole tools or accessories.

The ported sleeve assembly 22 can transition between three states: (i) aneutral position, which is shown in FIG. 1; (ii) a “shifted” position,as shown in and described with reference to FIG. 4; and (iii) an“actuated” position, as shown in and described with reference to FIG. 5.When used with reference to a normally-closed ported sleeve assembly,“actuated” means that the ports are opened to allow radial flow of fluidtherethrough.

The ported sleeve assembly 22 comprises a top connection 28 threaded toa housing assembly 30 that includes a spring housing 32, a seal housing34 having an annular upper end 36, and a ported housing 40. A pluralityof radially-aligned ports 42 is disposed through the ported housing 40to provide a fluid communication path between the interior of the portedsleeve assembly 22 and the surrounding formation.

A sleeve 44 is nested and moveable longitudinally within the housingassembly 30. The sleeve 44 comprises a spring mandrel 46 having anannular shoulder 48 located at the upper end of the sleeve 44, and anupper seal mandrel 50 having an annular lower end 51. A compressionspring 62 is positioned within an annular volume defined by the annularshoulder 48 and the annular upper end 36 of the seal housing 34. In theneutral position shown in FIG. 1, the compression spring 62 is underapproximately three-hundred pounds of compression.

A plurality of circumferentially-aligned initiation elements (e.g.,shear pins) 41 extend through the ported housing 40 and engage thesleeve 44. The initiation elements are frangible upon application of apredetermined pressure by the sleeve 44.

The sleeve 44 further comprises a lower seal mandrel 52 having anannular middle shoulder 53, and an annular slotted member 54 positionedaround the lower seal mandrel 52 and fixed longitudinally between thelower end 51 of the upper seal mandrel 50 and the middle shoulder 53.The slotted member 54 fits snugly around the lower seal mandrel 52, butis freely rotatable thereabout. The sleeve 44 incorporates a valve seatassembly that has a seating element in the form of an annular innerengagement surface 39 that will seal with an appropriately sized andshaped restrictor element (e.g., wiper ball or dart), as will bedescribed infra. The engagement surface 39 comprises a first and secondopposing openings 39′, 39″.

As shown in FIG. 1A, the valve seat assembly includes a guide elementthat has a counting element. The counting element includes a guidingmember, such as a torque pin 56, and a slot 58 formed in the exteriorsurface 60 of the slotted member 54. The torque pin 56 is fixed relativeto, and extends through, the ported housing 40.

The torque pin 56 is positioned within the slot 58. FIGS. 2A-2C show theslotted member 54 and the slot 58 in more detail. The slot 58 is acontinuous path formed of intersecting discrete, straight path segments,the path extending radially around and formed in the exterior surface 60of the slotted member 54. The intersections of the slot segments of theslot 58 form a repeated pattern of thirteen neutral positions 55 a-55 mand thirteen shifted positions 57 a-57 m positioned between a first end59 and a second end 61. The first end 59 of the slot 58 terminates inthe first neutral position 55 a. The second end 61 of the slot 58terminates with an actuated position 63 positioned downwell of theneutral positions 55 a-55 m.

The slot 58 is shaped so that when the torque pin 56 is in a neutralposition and the slotted member 54 moves downwell relative to the portedhousing 40 (in direction Ddw), the torque pin 56 moves, relative to theslotted member 54, toward the adjacent shifted position. For example,when the torque pin 56 is in the first neutral position 55 a and theslotted member 54 moves in direction Ddw, the torque pin 56 travelsalong the slot 58 to the first shifted position 57 a, where furtherdownwell movement of the slotted member 54 is impeded. When the torquepin 56 is in a shifted position, such as the first shifted position 57a, and the slotted member 54 moves upwell in direction Duw, the torquepin 56 travels toward the next adjacent neutral position, which is thesecond neutral position 55 b, or, if the torque pin 56 is at thethirteenth shifted position 57 m, to the actuated position 63.

Operation of the embodiment 20 is initially described with reference toFIG. 1. During installation, the embodiment 20 is positioned in awellbore with the torque pin 56 positioned at the first end 59 of theslot 58 (see FIG. 2C), which is in the first neutral position 55 a. Inthis neutral state or position, the sleeve 44 is positioned radiallybetween the plurality of ports 42 and the flowpath to prevent fluid flowto and from the surrounding formation.

As shown in FIG. 4, to shift the sleeve assembly 22 from a neutralposition to a shifted position, the well operator pumps a restrictorelement (e.g., ball) 80 downwell to the sleeve assembly 22. In theillustrated embodiment, the ball 80 is larger than the inner diameter ofthe seating element 39 that is the engagement surface of the sleeve 44.The ball 80 passes through the first opening 39′, which functions as aninlet, and seals to the engagement surface 39 of the sleeve 44, thuscreating a friction pressure against it. Although the expansive force ofthe compression spring 62 resists downwell movement of the sleeve 44,when the pressure differential across the ball 80 exceeds a firstpressure differential, the expansive force of the compression spring 62is overcome and the sleeve 44 moves to the second position shown in FIG.4, thus positioning the torque pin 56 in the next shifted position ofthe slotted member 54, depending on the position of the torque pin 56within the slot 58 prior to shifting. In this manner, the torque pin 56and slot 58 operate to keep a tally of the number times the pressuredifferential created across the ball between the inlet 39′ and theoutlet 39″ exceeds a first pressure differential by at least apre-determined amount. Because slot 58 contains a predetermined numberof slot positions the slotted member 54, torque pin 56 and slot 58 canbe used to effectively count the number of balls that are extrudedthrough the sleeve assembly 22 or the number of times a pressuredifferential is created between the inlet and the outlet exceeds a firstpressure differential by at least a pre-determined amount. Thepositioning of torque pin 56 and slot 58 in slotted member 54 indexesthe number of times the sleeve assembly 22 is shifted and tabulates thenumber using the positioning of torque pin 56 and slot 58 to enable aplurality of stages using multiple sleeve assemblies to be used becauseparticular sleeve assemblies can be actuated with precision and atpredetermined times or stages.

After the sleeve 44 has shifted, the continued pressure differentialwill extrude the ball 80 past the engagement surface 39 and through thesleeve 44. The compression spring 62 will thereafter expand to returnthe sleeve 44 to either a neutral or the actuated position, depending onthe position of the torque pin 56 within the slot 58 (see FIG. 2C).

As shown in FIG. 2C, the sequence described above is repeatable for thesleeve 44 until the torque pin 56 is positioned in the final neutralposition 55 m of the upper slot 58 m. Thereafter, the next ball passingthrough the sleeve 44 will move sleeve 44 and position the torque pin 56to move to the final shifted position 57 m of the slot 58. After theball passes through the sleeve 44 as described supra, the compressionspring 62 will urge the spring return 46 upwell until the torque pin 56is positioned in the actuated position 63. While the embodimentsillustrated in the figures show 13 neutral and shifted positions, anyplurality of neutral and shifted positions are contemplated in the scopeof the present invention. Further, the number of neutral and shiftedpositions are preferably the same, but differing numbers of neutral andshifted positions may be included in embodiments encompassed by theclaimed invention.

As shown in FIG. 5, when the first torque pin 58 is located in theactuated position 63 of the slot 58, the sleeve 44 is in a secondposition upwell of the ports 42, thereby permitting fluid flow into thesurrounding formation from the flowpath. In this state, the compressionspring 62 is under minimal, if any, compression.

Although the sleeve assembly 22 as described above requires thirteencycles to actuate the sleeve 44 to the second position if the torque pin56 is initially positioned at the first end 59 of the slot 58, thenumber of shifting cycles until actuation may be reduced by positioningthe sleeve assembly 22 in the wellbore with the torque pins 56positioned in one of the intermediate neutral slot positions 55 b-55 m.For example, the embodiment 20 may be preset to require only fourshifting cycles by setting the torque pin 58 to the tenth neutralposition 55 j prior to installation in the tubing string. Thus, passageof the fourth wiper ball will actuate the sleeve assembly 44 to thesecond position shown in FIG. 5. Moreover, slotted member 54 is notlimited to thirteen slot positions but rather the number of slots can beincreased or decreased.

FIG. 6 shows a system comprising three ported sleeve assemblies 22 a-22c installed in a formation production well drilled in a hydrocarbonproducing formation 100 that has three stages 100 a-100 c. Each of theported sleeve assemblies 22 a-22 c is configured to require a differentnumber of shifting cycles prior to actuating: the lower sleeve assembly22 c is located in the lower stage 100 c and is set to actuate after oneshifting cycle (i.e., the guiding member is initially positioned inneutral position 55 m of FIG. 2C); the middle sleeve assembly 22 b islocated in the middle stage 100 b and is set to actuate after twoshifting cycles (i.e., the guiding member is initially positioned inneutral position 55 l); and the upper sleeve assembly 22 a is located inthe upper stage 100 a and is set to actuate after three shifting cycles(i.e., the guiding member is initially positioned in neutral position 55k).

To fracture the surrounding formation 100, a first restrictor element ismoved through the tubing string and assemblies 22 a-22 c as describedsupra. Because the lower assembly 22 c is set to only require (i.e.,“count”) one shifting cycle for actuation, the lower assembly 22 c isopened to permit fluid flow into the surrounding formation 100. When asecond restrictor element is passed through the tubing string, themiddle ported assembly 22 b is opened. The area adjacent to the middleassembly 22 b may thereafter be fraced. When a third restrictor elementis passed through the tubing string, the upper ported sleeve assembly 22a is opened. The area adjacent to the upper sleeve assembly 22 a maythereafter be fraced. After fracturing, the well operator can producehydrocarbons through the assemblies 22 a-22 c and downwell of thedeepest assembly 22 c

The present invention also increases system effectiveness and reducesmechanical risk, thereby increasing system reliability while loweringcost. Operators need not be concerned about impacting the shifting ballinto a seat at too high of a rate or pressure which may lead in somecases to a failure of the ball or sleeve.

In one embodiment of a system incorporating the sleeve assembly, aported sleeve assembly is positioned as a bottom sub, or “toe sub,” in atubing string having a cemented liner. The assembly is cemented intoplace within the wellbore. Upon actuation of the ported sleeve assemblyfollowing the cycling of pressure through the tool as described supra,pressure may be increased to crack the cement sheath and establish fluidcontact to the formation.

In FIGS. 1-6, a valve seat assembly is incorporated into a ported sleeveassembly and described with reference to actuation of a ported sleevefor use in fracturing application. The valve seat assembly describedsupra, however, may be used to actuate any number of downhole tools,including flapper valves, stimulation devices, packers, and the like.

FIG. 7, for example, shows a section of a sleeve assembly as describedsupra that further comprises propellant stimulation components. Morespecifically, FIG. 7 is a side sectional view of a detonator assembly158 and a firing pin 190 positioned with a pressure chamber 154 formedin the assembly. One or more such pressure chambers 154 may bepositioned within the tool.

The firing pin 190 is within pressure chamber 154 proximal to an inlet155, and is retained in position by a firing pin locking key 176 engagedwith a retention groove 200 circumferentially disposed around the firingpin 190. A first end 188 of the firing pin 190 is pressure isolated froma second end 189 with a sealing ring 202. The inlet 155 of each chamber154 provides a fluid communication path to the flowpath.

The detonator assembly includes a primer 192, primer case 194, shapedcharge 196, and an isolation bulkhead 198. The primer 192 is spacedabove the firing pin 190 within the primer case 194. The shaped charge196 is positioned above and adjacent to the primer case 194. Theisolation bulkhead 198 is positioned adjacent the shaped charge 194 andproximal to the propellant volume 146. In this position, detonation ofthe shaped charge will cause corresponding ignition of the propellantvolume 146.

Downwell movement of the sleeve 44 causes hydraulic actuation of thefiring pin 190 by allowing the firing pin locking key 176 to radiallycontract into a groove formed into the exterior surface of the sleeve44. This contraction causes the firing pin locking key 176 to disengagefrom the firing pin 190.

Pressure thereafter communicated into the pressure chamber 154 causesthe firing pin 190 to move upwell because of the pressure differentialabove and below the sealing ring 202. In other words, because pressureupwell of the sealing element 202 is atmospheric, hydraulic pressurebelow the sealing element applies a hydraulic force on the second end189 of the firing pin 190 resulting in upwell movement. While the toolillustrated by the figures shows a sleeve for use in connection with aported housing, such ported housing is not a required element of theclaimed invention. A sleeve of any size, type or shape may be usedprovided that it, by its relationship with a valve seat, allowsactivation of the propellant stimulation components in response to apressure drop across the valve seat.

FIG. 8 shows the detonator assembly 158 with the pressure chamber 154after the firing pin locking key 176 has released the firing pin 190 andat the point of contact of the firing pin 190 with the primer 192. Thesealing ring 202 between the first end 188 and second end 189 of thefiring pin 190 isolates pressure in the pressure chamber 154 upwell ofthe sealing ring 202 from the pressure in the flowpath. After ports 174are aligned with the inlet 155, pressure within the flowpath iscommunicated through the ports 174 into the pressure chamber 154 at aposition below the sealing element 202, resulting in a pressuredifferential that moves the firing pin 190 upwell to contact anddetonate the primer 192. Detonation of the primer 192 is contained bythe case 194 and causes detonation of the adjacent shaped charge 196,which transfers explosive energy to the propellant volume 146, causingignition thereof. The explosive energy is directed radially outwardly inthe form of pressure waves and into the surrounding formation. By use ofthe valve seat assembly described herein, detonation may be timed toactuate following a preset number of pressure increases resulting fromseating, and subsequent passage, of a restrictor element between thefirst and second openings 39′, 39″ of the engagement surface 39.

FIG. 9 shows a tool 320 actuatable by a valve seat assembly having aslotted sleeve 348 and a torque pin 400. The tool 320 comprises ahousing 322 connected to a bottom connection 324 at a threaded section326. The housing 322 has a plurality of radially-oriented,circumferentially-aligned ports 328 providing communication paths to andfrom the exterior of the tool 320.

The housing 322 has a first cylindrical inner surface 330 having a firstinner diameter, a second cylindrical inner surface 332 located downwellof the first inner surface 330 and having a second inner diameter thatis greater than the first inner diameter, and a third cylindrical innersurface 334 having a third inner diameter that is greater than thesecond cylindrical inner surface 332. The first inner surface 330 islongitudinally adjacent to the second inner surface 332, forming adownwell-facing shoulder having an annular shoulder surface 338. Thesecond and third inner surfaces 332, 334 are separated by apartially-conical surface 340.

The tool 320 comprises an annular sleeve 348 nested radially within thehousing 322 and positioned downwell of the shoulder 338. The sleeve 348has an upper outer surface 350 with a first outer diameter and a secondouter surface 352 with a second outer diameter less than the first innerdiameter. The first outer surface 350 and second outer surface 352 areseparated by an annular shoulder surface 354. The sleeve 348 furthercomprises a cylindrical inner surface 356 that extends between annularupper and lower end surfaces 358, 360 of the sleeve 348.

The tool 320 may further comprise a guide element to position theseating element of the valve assembly at the desired location. The guideelement in the embodiment of FIG. 9 is a spring 364 residing in anannular spring return space 362. The annular spring return space 362 ispartially defined by the second outer surface 352 of the sleeve 348 andthe third inner surface 334 of the housing 322. The spring return space362 is further defined by the upper end surface 347 of the bottomconnection 324, the partially-conical surface 340 of the housing 322,and the shoulder surface 354 and first outer surface 350 of the sleeve348.

In the embodiment illustrated by the figures, a C-ring 370 is positionedwithin the annular sleeve 348 between the upper end surface 358 and theshoulder surface 354. The C-ring 370 fits into a groove formed in theinner surface 356 of the shifting sleeve 348. The groove is sufficientlydeep to allow the C-ring seating surface to expand to the desiredmaximum diameter. In some embodiments, the desired maximum diameter maybe as large as or larger than the inner diameter of the shifting sleeve.Those of skill in the art will appreciate that, in embodiments in whichthe C-ring 370 activates a sleeve or other valve assembly, the C-ring 70may be positioned at any point along the sleeve or tool, or above orbelow the sleeve, provided that the C-ring 370 and the sleeve 348 orother tool are connected such that sufficient pressure applied to theC-ring 370 will slide the sleeve in relation to the inner housing orotherwise activate the tool.

The C-ring 370 has an inner surface 374 an outer surface 376 definingthe outer perimeter of the C-ring 370, and a seating surface 372engagable with a restrictor element (e.g., a ball or dart) having acorresponding size. In the illustrated embodiment, the C-ring 370 isheld in a radially compressed state by the first inner surface 350 ofthe housing 322.

The valve seat assembly includes a guide element that has a countingelement, a timing element, an indexing element or other device forrecording or reflecting the restrictor elements which engage and passthrough the assembly or for recording or reflecting the pressure dropswhich occur across the valve seat which exceed a pre-determined value.In certain embodiments, such as the embodiment illustrated in FIG. 9, acounting element includes a guiding member, such as a torque pin 400,and a slot 402 formed in the exterior surface 361 of the sleeve 348. Thetorque pin 400 is fixed relative to, and extends through, the housing322 and bottom connection 324.

In FIG. 9, the torque pin 400 is positioned in a “neutral” position ofthe slot 402, which is identical to the slot shown in and described withreference to FIGS. 2A-2C and is a continuous path formed of intersectingdiscrete, straight path segments. The slot 402 extends radially around,and is formed in, the exterior surface 361 of the sleeve 348. Theguiding element is positioned in a neutral position of the slot 402,with the upper end 358 of the sleeve 348 positioned below the ports 28.

As indicated with reference to FIGS. 1-6, the sleeve 348 can transitionbetween three positions: (i) a neutral position, which is shown in FIG.9; (ii) a “shifted” position, as shown in and described with referenceto FIG. 12; and (iii) an “actuated” position, as shown in and describedwith reference to FIG. 14. When used with reference to a normally-openported sleeve assembly, “actuated” means that the ports are closed toinhibit radial flow of fluid therethrough.

As those of skill in the art will appreciate, the position of torque pin400 within the slotted sleeve 348 reflects the number of pressure dropsof a pre-determined value which must occur across the C-ring 370, (e.g.the valve seat) before a subsequent pressure drop of will causeactuation of the associated tool. In practice, such pressure drops arecreated by engaging the C-ring 370, or other valve seat, with arestrictor element. The valve seat thereby “counts” the number ofrestrictor elements passing the valve seat by indexing from one neutralposition to the next. Such counting occurs as a restrictor elementengages with the valve seat, enables formation of the required pressuredrop, the sleeve moves to the next shifted position, the restrictorelement releases from the valve seat, and the sleeve moves, by force ofthe spring, to the next neutral position. This cycle is repeated withsubsequent restrictor elements configured to create the necessarypressure drop across the valve seat (e.g. restrictor elements of theappropriate size and material). In this fashion, the guide elementaffects the actuation of the tool by indexing from neutral position toneutral position and thereby, in conjunction with the seating elementand restrictor element, controls the timing for actuation of the tool.

FIG. 10 shows a front elevation of one embodiment of the C-ring 370 in anormal uncompressed state. In this embodiment, the outer surface 376 ofthe C-ring 370 is castellated with a plurality of radial protrusions378, said radial protrusions defining the outer diameter of the C-ring370. The circumference of the outer surface of the C-ring 370 may belarger than the circumference of inner surface 356 of the sleeve 348.The C-ring 370 has a machined slot 380 forming terminal ends 382. Theslot 380 shown in the illustrative figures is within a protrusion 378,but the slot 380 may be formed at any point along the C-ring 370 anddoes not have to be formed in a protrusion 378.

Referring to FIG. 11, each of the radial protrusions 378 of theillustrated C-ring 370 is aligned with and extends through an opening384 in the sleeve 348 between the first outer surface 350 and the innersurface 356. When the C-ring 370 is upwell of the partially-conicalshoulder 340 of the housing 322, the C-ring 370 has the operatingdiameter shown in FIG. 11 and terminal ends 382 of C-ring 370 are incontact to form the seat defined by the seating surface 372. Anassociated restrictor element may thereafter seat against the seatingsurface 372 and a pressure differential created across the restrictorelement to move the sleeve 348 in the downwell direction.

FIGS. 12-13 show the tool 320 with the sleeve 348 in a shifted position,which is downwell of the position shown in FIG. 9. The coil spring 364is under compression between the sleeve 348 and the bottom connection324, with the upper end coil 366 of the spring 364 in contact with thesleeve shoulder 354 and the spring lower end 368 is in contact with theupper end surface 347 of the bottom connection 324. In this position,the spring 364 exerts an expansive force to urge the sleeve 348 in theupwell direction relative to the bottom connection 324. The torque pin400 is positioned in a “shifted” position of the slot 402.

Referring to FIG. 13, the C-ring 370 is positioned adjacent to thesecond inner surface 334. Because the second inner surface 334 has alarger diameter than the first inner surface 332, the C-ring 370radially expands towards its uncompressed shape shown in FIG. 10. Theprotrusions 378 extend past the outer surface 350 of the sleeve 348,opening the seating surface 372 and allowing the associated restrictorelement to pass through the C-ring 370, after which the spring 364pushes against the sleeve shoulder 354 to move the sleeve 348 upwell.

FIG. 14 shows the sleeve 348 in an actuated position in which fluid flowto the exterior of the tool 320 is inhibited by the sleeve 348. TheC-ring 370 is held in a closed state by the second inner surface 332 ofthe housing 322. The torque pin 400 is positioned in an “actuated”position of the slot 402. In one alternative embodiment, the C-ring 370may be adjacent to an additional inner surface, not shown, which issufficiently large to allow the C-ring to expand into its uncompressedstate. Further, the claimed invention also encompasses embodiments inwhich the valve assembly is moved to the actuated position by downwellmovement past the shifted position. In such an embodiment, a devicewhich locks the valve assembly in the actuated position may be desirablein order to hold the valve assembly in place against the force of thespring 364.

In some embodiments, a retaining element, not shown, may be placed inthe sleeve to define this intermediate position, such retaining elementbeing set such that it stops movement of the C-ring 370 and sleeve up toa first pressure, but allows movement of the C-ring 370 at a secondpressure. Those of skill in the art will appreciate that many retainingelements such as a shear ring, shear pins, or other device may be usedin conjunction with the valve assemblies described herein. Further,mechanisms, assemblies, methods or devices other than a retainingelement may be used for defining the intermediate third position in avalve assembly and any such method or element is within the scope of thevalve assemblies contemplated herein.

Yet another embodiment contemplates a seating element separatelyattachable to the interior surface of a sleeve and operable with aresilient restrictor element, such as the valve seat assembly shown inU.S. application Ser. No. 13/423,154, filed Mar. 16, 2012 and entitled“Downhole System and Apparatus Incorporating Valve Assembly WithResilient Deformable Engaging Element,” and which is incorporated byreference. In this embodiment, the restrictor element has a resilientportion with a first shape when no more than a first pressuredifferential is applied across said restrictor element in a directionand a second shape when a second pressure differential is applied acrossthe restrictor element in the same direction. The restrictor element isengagable with the seating element to substantially prevent fluidcommunication through said sealing section when a pressure differentialis applied to the restrictor element that is less than the firstpressure differential. The restrictor element is extrudable through saidseating element without substantial permanent deformation by applying atleast a second pressure differential.

According to another embodiment of the invention, the seating elementmay comprise a plurality of seat segments interconnected with at leastone elastomeric member, as disclosed in U.S. application Ser. No.12/702,169, filed Feb. 28, 2010 and entitled “Downhole Tool WithExpandable Seat,” which is incorporated by reference herein. In thisalternative embodiment, the seating element is moveable between a firstsection of a housing, said first section having a first inner diameter.The housing has a second section downwell from said first section andhaving a second inner diameter greater than said first inner diameter.The first inner diameter is sized to prevent expansion of the seatingelement when the seating element is positioned in said first section,whereas the second inner diameter is sized to allow expansion of theexpandable seat when in the second position. Any other valveseat-restrictor element combination is within the scope of the claimedinvention provided such combination allows the creation of a desiredpressure drop across the valve seat, the release of the restrictorelement past the valve seat, and the restrictor element is substantiallyundamaged or otherwise not deformed such that it can form a fluid sealwith a subsequently engaged valve seat.

The apparatus and systems are described in terms of embodiments in whicha specific system and method are described. Those skilled in the artwill recognize that alternative embodiments of such system, andalternative applications of the method, can be used. Other aspects andadvantages may be obtained from a study of this disclosure and thedrawings, along with the appended claims. Moreover, the recited order ofthe steps of the method described herein is not meant to limit the orderin which those steps may be performed.

1. A valve seat assembly for use in a well for oil, gas or otherhydrocarbons, said valve assembly comprising: a seating element havingan inlet and an outlet; and a counting element; wherein said countingelement is configured to keep a tally of the number times a firstpressure at the inlet exceeds a second pressure at the outlet by atleast a pre-determined amount.
 2. The valve assembly of claim 1 furthercomprising an initiation element configured to prevent said countingelement from keeping said tally until after such initiation element isactuated.
 3. The valve assembly of claim 1 further comprising anactivation element, wherein said activation element is configured toactuate a downhole tool when said tally reaches a desired number.
 4. Thevalve assembly of claim 1 further comprising: an restrictor element witha resilient portion having a first shape when no more than a firstpressure differential is applied across said engaging element in adirection and a second shape when a second pressure differential isapplied across the restrictor element in the direction; wherein saidrestrictor element is engagable with the first seating element tosubstantially prevent fluid communication through said sealing sectionwhen a pressure differential is applied to the restrictor element thatis less than the first pressure differential; and wherein saidrestrictor element is extrudable through said seating element withoutsubstantial permanent deformation by applying at least the secondpressure differential.
 5. The valve seat assembly of claim 1 whereinsaid seating element comprises: a plurality of seat segmentsinterconnected with at least one elastomeric member, and wherein saidseating element is moveable between a first section of a housing, saidfirst section having a first inner diameter, and said housing furthercomprises a second section downwell from said first section and having asecond inner diameter greater than said first inner diameter; andwherein said first inner diameter is sized to prevent expansion of saidexpandable sleeve when said expandable sleeve is positioned in saidfirst section, and said second inner diameter is sized to allowexpansion of said expandable sleeve when said expandable sleeve is insaid second section.
 6. The valve seat assembly of claim 1 furthercomprising: an annular sleeve having an inner surface with a diameter, afirst cylindrical outer surface, and a plurality of openings extendingbetween said inner surface and said first cylindrical outer surface,wherein said annular sleeve further comprises a second cylindrical outersurface having a different diameter than the first cylindrical outersurface; wherein said seating element comprises a first C-ring having abody with a seating surface, opposing terminal ends, and an outerdiameter extending from the body, wherein the first C-ring is at leastpartially within the inner surface of the sleeve; and a coil springpositioned around a portion of the sleeve and in an annular space atleast partially defined by an annular body and the second cylindricalouter surface.
 7. The valve assembly of claim 1 wherein said countingelement comprises a slotted sleeve.
 8. The valve assembly of claim 1wherein said counting element comprises a slotted sleeve having aplurality of neutral positions, a plurality of shifted positions, and atleast one actuated position.
 9. A valve assembly for use in a well foroil, gas or other hydrocarbons, said valve assembly comprising: aseating element, said seating element comprising an inlet and an outlet;and a counting element; wherein said counting element is configured tokeep a tally of restrictor elements of a desired size range anddeformability range that pass through said seating element.
 10. Thevalve assembly of claim 7 further comprising an initiation element, saidinitiation element configured to prevent said counting element fromkeeping said tally until after such initiation element is actuated. 11.The valve seat assembly of claim 7 further comprising an activationelement, wherein said activation element is configured to actuate adownhole tool when said tally reaches a desired number.
 12. A valve seatassembly for use in a well for oil, gas or other hydrocarbons, saidvalve seat assembly comprising: a path for the flow of fluids throughthe valve seat assembly; a seating element configured to receive arestrictor element and thereby reduce or eliminate the flow of fluidsthrough the path; a guide element comprising: a counting elementconfigured to keep a tally of restrictor elements having desiredcharacteristics that pass through said seating element, and anactivation element, wherein when said tally reaches a predeterminedvalue, said activation element is actuated and said valve assemblyactuates a tool in communication with said assembly.
 13. The valveassembly of claim 10 wherein said counting element is a slotted sleeve.14. The valve assembly of claim 10 where said initiation element is ashear pin.
 15. A valve assembly for use with a downhole tool, said valveassembly comprising: a seating element, said seating element comprisingan inlet and an outlet, and a guide element having a counting member;wherein said seating element is configured to engage a restrictorelement and thereby reduce or prevent the flow of fluid from said inletto said outlet, said seating element is engaged with said guide elementsuch that said guide element is configured to prevent actuation of saidtool through a first cycle of pressure increase and decrease; and saidguide element is configured to permit actuation of said tool during anactivation cycle, which occurs subsequent to said initiation cycle. 16.The valve assembly of claim 13 further comprising a plurality ofrestrictor elements.
 17. The valve assembly of claim 13 wherein saidguide element is configured to prevent actuation of said tool through aplurality of indexing cycles.
 18. A downhole tool for use in aproduction well having a tubing string defining a flowpath, the downholetool comprising: a ported housing having a plurality of ports disposedradially therethrough; a sleeve at least partially within said portedhousing and moveable between a first position and a second position,wherein in said first position said sleeve is radially positionedbetween said plurality of ports and said flowpath, said sleeve having anupper end, an exterior surface, a slot formed in said exterior surface,and an engagement surface having a first inner diameter; a guidingmember fixed relative to said housing and positionable within said slot;and a compression spring positioned between said upper end of saidsleeve and said ported housing, said compression spring being undercompression when said sleeve is in said first position.
 19. The downholetool of claim 16 further comprising: a C-ring having first and secondterminal ends defining a split and a plurality of radially-extendingprotrusions, said C-ring being moveable between a compressed state,wherein the ends of the C-ring are in contact to form a closed seat, andan uncompressed state; wherein said sleeve has an interior surface, anexterior surface, and a groove formed in said interior surface with aplurality of openings extending between said interior and exteriorsurfaces, said openings aligned to receive with said plurality ofradially extending protrusions; wherein said housing has a first insidediameter and a second inside diameter that is larger than said firstinside diameter; wherein when said groove is positioned within saidfirst inside diameter, said protrusions hold said C-ring in an at leastsubstantially compressed state; and wherein when said groove ispositioned within said second inside diameter, the C-ring is in an atleast substantially uncompressed state.
 20. The downhole tool of claim17 further comprising: a propellant volume; an annular portion with atleast one pressure chamber having an end positioned adjacent to saidpropellant volume and an inlet providing a communication path to saidflowpath; at least one detonator assembly within said at least onepressure chamber proximal to said end; at least one firing pin withinsaid at least one pressure chamber, said at least one firing pin havinga first end pressure isolated from a second end; a second section havinga plurality of flow ports defining a fluid communication path betweensaid flowpath and the exterior of the downhole tool; wherein said sleeveis moveable between a first position and a second position, wherein insaid first position said sleeve assembly is between said plurality offlow ports and said flowpath and between the inlet of said at least onepressure chamber and said flowpath.
 21. A system for producinghydrocarbons from a well wherein the downhole tool of claim 16 ispositioned as a bottom sub.
 22. A valve seat assembly for use in a wellfor oil, gas or other hydrocarbons, said valve assembly comprising: aseating element having an inlet and an outlet; and a guide element;wherein said guide element is configured to reflect the number times afirst pressure at the inlet exceeds a second pressure at the outlet byat least a pre-determined amount.
 23. The valve seat assembly of claim22, said guide element further comprises a timing element wherein saidtiming element causes actuation of a tool when the number of times saidfirst pressure exceeds said second pressure by at least a pre-determinedvalue reaches a desired number.
 24. The valve seat assembly of claim 22,said guide element further comprises a timing element wherein saidtiming element allows actuation of a tool when the number of times saidfirst pressure exceeds said second pressure by at least a pre-determinedvalue reaches a desired number.
 25. An assembly for actuating a downholetool in a production well having a tubing string defining a flowpath,the assembly comprising: a housing; an annular body at least partiallywithin said housing and moveable between a first position and a secondposition, said annular body having an upper end, a lower end, anexterior surface, a slot formed in said exterior surface; a guidingmember fixed relative to said housing and positionable within said slot;and a spring positioned between said upper end of said annular body andsaid housing, said spring being under compression when said annular bodyis in said first position; wherein said slot has a continuous pathbetween a first and second end formed of intersecting segments forming arepeated pattern of circumferentially-aligned first positions andcircumferentially-aligned second positions positioned between said firstend and said second end, and wherein the first end intersects one ofsaid first positions and said second end is positioned longitudinallybetween said first positions and said lower end of said annular body.26. The assembly of claim 25 wherein said annular body is a sleevehaving a seating element with an engagement surface having an innerdiameter sized to engage with a corresponding restrictor element. 27.The assembly of claim 25 wherein said annular body is a slotted memberfixed relative to a seating element with an engagement surface having aninner diameter sized to engage with a corresponding restrictor element.